Bulldozers conventionally carry at their front ends a large ground-engageable blade, for scraping granular material (earth, snow, . . . ) from the ground or for leveling the latter. The blade is supported in generally vertical position, with its bottom edge destined to engage the ground. The blade height is usually controlled by a first ram means, while the relative inclination of the blade can be controlled by a second ram means. In some bulldozers, third ram means are provided to lift one lateral end of the blade relative to the opposite lateral end, to expand the capabilities of the bulldozer: e.g. to work with a corner only of the blade to unearth a large ground-embedded rock, or to provide an inclined bottom leading edge to produce a radially outwardly raised ground surface in a curved section of a snow-based road.
For example, U.S. Pat. No. 2,839,849 issued in 1958 to Clark Equipment Co., discloses thrust means 78 at the mid portion of a bulldozer blade 58, being adapted to resiliently deform or warp the blade forwardly or rearwardly to effect a downward or upward tilting movement of the cutting edge of the blade. These thrust means consists in a hydraulic ram 78 located between the two main, blade lifting, hydraulic rams 100, 106. Opposite lateral telescopic struts 150, 170 load the blade to the chassis of the bulldozer. The bulldozer operator, by engaging a pin 186 into a slot of telescopic strut 170, and energizing intermediate ram 78, will bias the blade in becoming warped since the unlocked strut 150 can extend but not the locked struts 170, whereby the lateral end of the blade in register with the opposite strut 150 will lift. Such a procedure is inefficient, in that the operator must leave his seat in the bulldozer cabin to engage or release the pin 186, each time lateral tilting of the bade is required. Moreover, warping of a blade is possible only if this blade is made sufficiently flexible and thin, which thus limit its durability and reduce the maximum load capability of the blade. Indeed, it is obvious that blade warping will tend to compromise the structural integrity of the blade, with time and wear.
U.S. Pat. Nos. 3,653,451 issued in 1972 to Caterpillar tractor co., and No, 4,019,588, are similar to the above-noted patent in that they provide lateral tilt capability for a blade thanks to blade warping means.